Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $57.48   9.364%   $62.8624   $62.86   $62.85   $62.90  
  Purchase #2 $187.89   10.366%   $207.3667   $207.37   $207.35   $207.40  
  Purchase #3 $241.90   3.394%   $250.1101   $250.11   $250.10   $250.10  
  Purchase #4 $98.37   6.780%   $105.0395   $105.04   $105.05   $105.00  
  Purchase #5 $207.82   11.628%   $231.9853   $231.99   $232.00   $232.00  
  Purchase #6 $104.43   12.836%   $117.8346   $117.83   $117.85   $117.80  
  Purchase #7 $62.93   8.193%   $68.0859   $68.09   $68.10   $68.10  
  7 purchase totals = $960.82       $1,043.2845   $1,043.29   $1,043.30   $1,043.30